Method of curing-rubber and product resulting therefrom



compounds of *sulfena'mide's which Patented July 19 1949 METHOD OF CURING;RUBBEB -;AND;PROD- Uc'r RESULTING :T-HEREF-ROM Edward LiCarr, Akron, Ohio, and John Richard Rafter, Sharon, Mass., assignors to The Firestone Tire & Rubber Company, Akron, Ohio, at

V corporation-phonic No'Drawing. Application March 20,;1945, Serial N0. 583,858

This-inventionrelates' to metal-halide 'adiiition I are {accelerators-of the vulcanization of rubbers. Exampli'es are the metal-halide addition -compounds of the thiazolinyl sulfena'mide's, the metal-halide "add'r- 'tion compounds of the thiazyl sul'fenamides, ahd 'the metal-halide additioncompoun'd's o'f th'e this; carbamyl sulfenamides. They are represented by the following formulae:

and MX2 is a-complex form-ing halide-saltmfa bivalent metal, such as zinc, copper, :cadmium, etc" and X is chlorine, bromine 101' iodine. thermore, in Formula II the R" .imaiy coined with the double-bonded carbons to formiantapyl ene group, such as benzo-, -tetrahydrobenzo-,.etc., and in Formula III the R" and :R may join with the nitrogen to form a rhQtfiIiOCYCliCaQI'QUDEilE-l which R"R"' is alkylene or .alkylene-oxyaalkylene, such as piperidyl, morpholyl, etc.

Typical compounds are the zinc-chloride, etc., addition compounds of:

N-furfuryl thiazolinyl sulfenamide N-methyl thiazolinyl sulfenaniide N,N--diethyl thiazolinyl sulfenamide N-cyclohexyl thiazolinyl sulfenamide N-cyclohexyl-L-methyl thiazolinyl sulfenamid'e -N-cyclohexyl 4,5-dimethyl thiazyl :sulfena'mid'e -N-isopropyl-4,'5 dimethyl thiazyl suI-fenamitle N -cyclohexyl-4'-ethyl thiazy-l sulfe'namide N-e'thyl--ethyl thiazyl 'sul fcn'amide reaction has taken place.

'N,'N-diethyl 4f5 diiiiethyhthiazyl sulfenamide N ,N-ditetrahydrofurfhWl thiazyl s ulfen-ainide- *NgN'fdiGfihYl diethylthiocarbamyl sulfenamide N -rcyclopentamethylene cyclopentamethylene thiocar-bamyl sulfenamide V N-:cyclohexyl dimethylthiocarbamyl sulfenamide aN,N-dicyclohexyl naphthothiazyl sulfenamide FN-iiSODIfQDYl benzothia zyl sulfenamide N-cyclohexyl benzothiazyl sulfenamide N-"methyIbeIIZdthia'ZyI sulfnamide 'NZN 'ditetrahydrofurfu'ryl di'tetiahydrofuffiiryl thioica'rb'aniyl sulfenan'lide Eacho'f the above m'eritioned sulieriamidcsniay :be produced by any of the usual swans-mistreactions "which "employ water-soluble amines. Howeven the invention isnot limited to such sulfenamides but includes-the addition products of allsulfenamides suitable for use in plastics. Sul- -fenamides produced from insolubleamines, such as 's ulfenamides with aromatic substitu'ents, long Ichai'n aliphatic substituents, eZtc., mayfb ,produced :by metathesis. ,For example, N dodecyl penzotliiazyl-sulfenanuae maybe jprodiicejd by dissolving benzothiazyl sulfenamide in dodecyl amine and allowing the ,mixtureto stand untii'the m a E eew thiazolinyl .sulfenamide, -l I-'tol yl fthiazyi sulfen amide, and N-phenyl dimethyl canbamyl sulfen- .amide vareillustrative of aryl substituted com- ;.pounds formed-in this manner from whichmetal halide-complexespf thisinuentionmay be-fcrmed. I he zinc-chloride addition products are accelerators 'of the vulcanization of natural rubber. JI he formation of the complex L permits converting a low-melting or liquid sulfenamide into a higher-melting or solid compound, thus rendering the accelerator more stable "or more easily handled. Theaddition products give -a slower cure than :the sulfenamides from xwhi-chthey are formed and are delayed-action accelerators. The vulcanized products are different from those 'pro- 'duced with the 'siilfenamides. "For instance, the zinc-chloride addition compounds give "a lower modulus natural rubber stock than the parent sulfenamides and may be used in obtaining softer stocks. I a

Qthe'r s'alts, such as the cupri-c chIoi-ide salts, may be used in -the v ul'c'ahizaition"of synthetic ru'bbe'r s, elic Suo-h a's' the r-ubbr likecopolymr e f butadine-ahd-styrene, in which pepper dei i atitles have no detriiiien'tal efi'eot. 'I h'e murmur-n "Salts may be used in curing rubber ah'd rub-perlike materials.

Ihe rclmwm examples are typical and trate the preparation of different complexes from N-cyclohexyl benzothiazyl sulfenamide:

Example 1 An ether solution of N-cyclohexyl benzothiazyl sulfenamide was mixed with an ether solution of zinc chloride. The proportions of reactants were 2 mols sulfenamide to 1 mol zinc chloride. Im-

The melting point of the parent sulfenamide is 100-102 C.

The addition product was tested in rubber, using the corresponding sulfenamide as a control. The formula employed was:

Parts Smoked sheet 100 Sulfur 3 Zinc oxide 5 Stearic acid 1.10 Accelerator 0.75

The stocks were cured at two different temperatures for varying lengths of time. The time is expressed in minutes in the following table, which gives the modulus and tensile strength for the control and the test material in pounds per square inch:

600% Modulus Tensile at Break Cured at 240 F.:

Control 750 1800 2650 3600 Test material 375 -l 2100 Cured at 280 F.:

Control 2500 2300 1825 3725 3675 3425 Test material 1350 1525 1300 3550 3250 3425 For the preparation of cupric salts, some other solvent than ether will be preferred, as, for example, ethyl alcohol.

Earample 2 Seventeen grams CuC1a2I-I2O were dissovled in 100 cc. ethyl alcohol to a, dark green, clear solution. Fifty-three grams N-cyclohexyl benzethiazyl sulfenamide were dissolved in 700 cc. ethyl alcohol to which was added 100 cc. benzene. The mixture immediately became dark in color, and after a few minutes a chocolate-brown solid separated out. The solid was washed twice with ether. The melting point of the product, N- 75 RR is selected 4 cyclohexyl benzothiazyl sulfenamide cupric chloride, was 160 C.

What we claim is:

1. The method of curing rubber which comprises-reacting the rubber with sulfur in the presence of an accelerator selected from the class of compounds having the formula RI! R t-N \C-SNRR' where R is selected from the group of radicals consisting of hydrogen, furfuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, where R. is selected from the group of radicals consisting of hydrogen, furfuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, also where NRR' is a heterocyclic radical in which RR is selected from the group consisting of alkylene and alkylene-oxy-alkylene; where R" is selected from the group of radicals consisting of hydrogen, furfuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, and MXz is a complex-forming salt in which M is a bivalent metal and X is a halide radical of the class consisting of chloride, bromide and iodide.

2. The method of curing rubber which comprises reacting the rubber with sulfur in the presence of an accelerator selected from the class of compounds having the formula where R is selected from the group of radicals consisting of hydrogen, furfuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, where R is selected from the group of radicals consisting of hydrogen, furfuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, also where NRR. is a heterocyclic radical in which RR. is selected from the group consisting of alkylene and alkylene-oxy-alkylene; where R" is selected from the group of radicals consisting of hydrogen, furfuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydocarbon aryl and hydrocarbon aralkyl, also where the two R form with the double-bonded carbons a radical from the group consisting of arylene and partially hydrogenated arylene; and MX2 is a complex-forming salt in which M is a bivalent metal and X is a halide radical of the class consisting of chloride, bromid and iodide.

3. The method of curing rubber which comprises reacting the rubber with sulfur in the presence of an accelerator selected from the class of compounds having the formula where R is selected from the group of radicals consisting of hydrogen, furfuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, where R is selected from the group of radicals consisting of hydrogen, furfuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, also where NRR' is a heterocyclic radical in which from the group consisting of smears aikyl'ene and-aliiylene oxy -alkylene; where R -isselected from theroup ofradicals'consisti-n'g of hydrogen; f1'irfuryl; tetrahydrorurfuryl, hydro-' carbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, where R"' isselected iromthe group of radicalsconsistingofhydrogen; furfuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, also where NR""R"' is a heterocyclic radical in which R"R" is selected from the group consisting of alkylene and alkylene-oxy-alkylene; and MXz is a-complex form-ingsa-ltin which M is a bivalent metal and X is a halideradical of the-class consisting of chloride, bromide and iodide.

41A vulcanizabl-e rubber composition which contains an accelerator selectedfrom the class of compounds having the formula where R is selected-from the group of radicals selected from the group of radicals consisting of hydrogen, furfuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, and MXz is a complex-forming salt in which-M is a bivalent metal and X is a halide radical of the class consisting of chloride, bromide and iodide.

5. A vulcanizable rubber composition which contains an accelerator selected from the class of compounds having the formula where Ris selected from the group of radicals consisting of hydrogen, furfuryl, tetrahydrofur furyl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, where R" is selected from the group of radicals consisting of hydrogen, furfuryl, tetrahy'drofurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, also where NRR isv a heterocyclic radical in which RR is selected from. the group consisting of alkylene and alkylene-oxy-alkylene; whereR" is selected from the group of radicals consisting of hydrogen, furfuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, also where the two R" form with the double-bonded carbons a radical from the group consisting of arylene and partially hydrogenated arylene; 'and MX2 is a complex-forming salt in which M is a bivalent metal and X is a halide radical of the class consisting of chloride, bromide and iodide.

6. A vulcanizable rubber composition which contains an accelerator selected from the class of compounds having the formula RIII ].MX2

consistingor hydrogen: furfuryig tetrahydrofurfuryl, hydrocarbon al-kyl',- hydrocarbon aryl and hydrocarbon aralkyl, where R" is selected from the group of radicals consisting of hydrogen, furfuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, also where NRR' is a heterocyclic radical in which RR is selectedirom the group consisting of alhylene and. alkylene-oxy-alkylene;. where R." is selectedcfrom the group of. radicals consisting of hydrogen, furiuryhtetrahydroiurfuryl,. hydrocar-r bon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, where. R!" is. selectedfrom. thegroup of radicals consisting of. hydrogen, furiuryl, tetra.- hydrofurfuryl, hydrocarbon alkyL, hydrocarbon and hydrocarbon aralkyl also where NR R- is a, heterocyclie radical in which RIRZ" is. selected from. the group consisting. of alkylene and alkylene-oxy-a1kylene;..and MXz is ascomplex-forming salt which M is a, bivalent metal and X is. a halideradicalof the class consisting of chloride. bromide. andiodida 7. Rubber whichv has been cured with sulfur in the: presence of anacceleratortselected. from the class of compounds having the formula Rats (F's-4mm mix,

R" i 2. v

where R is selected from the group or radicals consisting of hydrogen, furfuryl tetrahydrofurfuryl, hydrocarbon alkyLhydrocarbon aryl and hydrocarbon aralkyl, where R is selected from the group of radicals consisting of hydrogen, furfuryl, tetrahydrofurfuryl', hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, also where NRR' is a heterocyclic radical in which RR is selected from the group consisting of alkylene andalkylene-oxy alkylene; where R" is selected from the group" of radicals consisting of hydrogen, furfuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydrocarbon 'aryl'and hydrocarbon aralkyl, and MXz is a complex-forming salt in which M is a bivalent metal and X is a halide radical of the class consisting of chloride, bromide and iodide.

"8. Rubber which has been cured with sulfur in the presenceof an accelerator sel'ectedfrom the class of compounds having the formula 1 where R is'selected from the group of radicals consisting of hydrogen, furfuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, where R is selected from the group of radicals consisting of hydrogen, iurfuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, also where NRR' is a heterocyclic radical in which RE is selected from the group consisting of alkylene and alkylene-oxy-alkylene; where R" is selected from the group of radicals consisting of hydrogen, furfuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, also where the two R" form with the double-bonded carbons a radical from the group consisting of arylene and partially hydrogenated arylene; and MX: is a complex-forming salt in which M is a bivalent metal and X is a halide radical of the class consisting of chloride, bromide and iodide.

9. Rubber which has been cured with sulfur in the presence oian accelerator selected from the class ofcompounds having the formula where R is selected from the group of radicals consisting of hydrogen, iuriuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, where R is selected from the group of radicals consisting of hydrogen, furiuryl, tetrahydroiurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, also Where NRR' is aheterocyclic radical'in which RE is selected from the group consisting of alkylene and alkyieneeoXy-alkylene; where R is selected from the group of radicals consisting of hydrogen, furfuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, where .R' is selected from the group of radicals consisting of hydrogen, furfuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon. araikyl, also where NRJ'R is a heterocyclic radical in which RR is selected from the group consisting of alkylene and alkylene-oxy-alkylene; and NXz is a complex-forming salt in which M is a bivalent metal and X is a halide radical of the class consisting of chloride, bromide and iodide.

10. The method of curing rubber which comprises reacting the rubber with sulfur in the presence of N-cyclohexyl benzothiazyl sulfenamide zinc chloride, as an accelerator. V V

11. A vulcanizable rubber composition which contains as an accelerator N-cyclohexyl benzothiazyl sulienamide zinc chloride.

12. Rubber which has beencured with sulfur in the presence of N-cyclohexyl benzothiazyl sulfenarnide zinc chloride, as an accelerator.

13. The method of curing rubber which comprises reacting the rubber with sulfur in the presence of an accelerator which is a complexforming bivalent-metal-chloride addition product of a sulfenamide of the group consisting of the unsubstituted and substituted-(a) thiazolinyl, (b) thiazyl and (c) thiocarbarnyl sulfenamides, the substituents being selected from the group of radicals consisting of furiuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, said sulfenamides consist ing of the class in which (1) the sulfenamide group is unsubstituted and in which (2) it is substituted by one substituent and inwhich (3) it is substituted by two substituents said substituents being of the class consisting of furfuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, and in which (4) the two N-hydrogens are replaced by a bivalent radical of the class consisting of alkylene and alkylene-oxy-alkylene.

14. A vulcanizable rubber composition which contains an accelerator which is a complex-forming bivalent-metal-chloride addition product of a sulfenamide of the group consisting of the unsubstituted and substituted(a) thiazolinyl, (b) thiazyl and (c) thiocarbamyl sulfenamides, the substituents being selected from the group of radicals consisting of iurfuryl, tetrahydroiurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, said sulfenamides consisting of the class in which (1) the sulfenamide group is unsubstituted and in which (2) it is substituted by one substituent and in which (3) it is substituted by two substituents said substituents being of the class consisting of furfuryl, tetrahydroiurfuryl, hydrocarbonalkyl, hydrocarbon aryl and hydrocarbon aralkyl, and in which (4) the two N hydrogens are replaced by a bivalent radicalof the class consisting of aikylene and alkylene-oxy-alkylene.

15. Rubber which has been cured with sulfur in the presence of an accelerator which is a compleX-forming bivalent-metal-chloride addition product of a sulfenamide of the group consisting of the unsubstituted and substituted-(a) thiazolinyl, (b) thiazyl and (c) thiocarbamyl sulfenamides, the substituents being selected from the group of radicals consisting of furfuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, said sulfenamides consisting of the class in which (1) the sulfenamide group is unsubstituted and in which (2) it is substituted by one substituent and in which (3) it is substituted by two substituents said substituents being of the class consisting of furfuryl, tetrahydrofurfuryl, hydrocarbon alkyl, hydrocarbon aryl and hydrocarbon aralkyl, and in which (4) the two N-hydrogens are replaced by a bivalent radical of the class consisting of alkylene and alkylene-oxy-alkylene.

EDWARD L. CARR. JOHN RICHARD RAFTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,823,499 Lutz Sept. 15, 1931 2,242,208 Davis May 20, 1941 2,271,834 Carr Feb. 3, 1942 2,284,578 Jones May 26, 1942 2,339,552 Carr Jan. 18, 1944 

